I’ve heard of parallax, but what actually is it?
Mark says: Parallax is something most shooters have heard of, but many don’t really understand. Basically, it is when your crosshair and your target are correctly focused, or ‘parallax free’.
To achieve this, when you first fit your scope, you should mount the rifle and view a plain background (clear sky is best), then adjust the eyepiece to bring the crosshairs sharply into focus. To correct for parallax, you will also need to be focused on your target.
Most scopes now have a parallax knob on the left side opposite the windage knob. It’s important to adjust this to focus on your target to correct for parallax. With crosshair and target in clear focus, you now have correct parallax.
So why is this important? Well, if you do not adjust this correctly and your head position on your stock varies with different shooting positions, you may not always be looking directly through the dead centre of your scope. If parallax isn’t correctly adjusted, your target will appear to move in relation to your crosshair with any slight head movement on the stock. This will move your point of aim and consequently point of impact on the target.
More basic scopes without the parallax adjustment will usually be factory set for parallax around 100-120 yards, though you will still need to focus your crosshairs to your own eye.